SPACES

\newlanguage\mylang
\def\my{\mylang}
\char\my 2

\char\mylang 2

%*
\def\ym{1}
\char\ym 2

\def\mm{1 }
\char\mm 2

\chardef\yy=1
\char\yy 2

%*
\def\xx{\chardef\zz=1}
\xx 2
\char\zz

\def\aa{\chardef\bb=1 }
\aa 2
\char\bb 3

\def\cc{\chardef\dd=1\relax}
\cc 2
\char\dd

\bye % ---------------------

\language4
\hyphenation{ab-cdef}

\language42
\hyphenation{abc-def}

\def\ff{
  \language4%
}
\ff 2
\showhyphens{abcdef} % language4

\def\gg{
  \language\mylang
}
\gg 2
\showhyphens{abcdef} % language4

\def\hh{\language4 }
\hh 2
\showhyphens{abcdef} % language42

UNICODE

http://www.endmemo.com/unicode/unicodeconverter.php
http://unicodelookup.com/
http://www.ltg.ed.ac.uk/~richard/utf-8.cgi
http://www.rapidtables.com/convert/number/binary-converter.htm

perl -C2 -le 'print pack("U0W*", hex("d0"), hex("81"))'

perl -Mutf8 -le 'print join " ", unpack("U0(H2)*", pack("U", ord "Ё"))'

klavaro fix

touch ~/.config/klavaro/preferences.ini